The present invention relates generally to copying machines or apparatus and particularly to a developer station of a copying machine and more particularly to a sealing assembly for sealing lead-in areas in a developer station of a copying machine in which a latent image is developed that has been established in a conductive material by an at least partly magnetizable mixture of developer powder transported towards the conductive material by means of a driven and rotating magnet drum and fed to the magnet drum from a supply. In side walls of a casing of the developer station shaft lead-in areas and bearings also for shafts are provided including feeding or mixing elements for the mixture of developer powder.
Copying machines of the above stated type and developer stations for such copying machines are already known. A developer station with a magnet drum in described in the German Laying-Open specifications Nos. 2,224,624 and 1,963,751. With magnet drums of the type described in the cited specifications there arises the problem that the mixture of developer powder that forms a brush at the field lines of the magnet drum and fed to the magnet drum from a supply, may escape at both sides of the magnet drum into the housing of the copying machine. Thereby the copying machine is contaminated. It has already been tried to have the ends of the magnet drum rotate in a sleeve made of a sealing material. A seal of this type, however, causes friction and is subject to wear so that a long term secure seal is not possible, quite apart from the drag resistance against rotation of the magnet drum.
With respect to the magnet drum, the invention relates to all prior art types of magnet drums, i.e. magnet drums with a rotating magnet system as well as magnet drums with a stationary magnet system wherein the magnet drum is surrounded by an encasing tube. In the latter case, the encasing tube is driven in a manner known per se.
The magnets of the magnet system extend, in these magnet drums, generally in the axial direction whereby the polarization alternates about the circumference of the magnet system, that is, of the magnet drum. Particularly in a magnet drum with an encasing tube it is known that the magnet system is somewhat shorter in axial direction than the encasing tube so that in the regions of the ends of the encasing tube there will not be formed a magnet brush or only a weak magnet brush, and exactly in these regions the risk of mixture of developer powder being thrown off or escaping into the housing of the copying machine is particularly great.
The mixture of developer powder consists of extremely fine particles of a pigment which performs the development proper, and fine iron particles serving as carrier for the pigment.
The magnet system of the magnet drum may be of a design that is different from the design indicated above. The arrangement with axially extending pole strips is especially advantageous and is preferred.
In developer devices of the stated type there is arranged a trough shaped supply reservoir for the mixture of developer powder underneath the magnet drum and optionally laterally offset thereto. Intermediate this supply reservoir and the magnet drum may be disposed feeding means of various designs, such as in the form of a cup or pump unit which drops the mixture of developer powder from above onto the magnet drum. Alternatively the feeding means can be in the form of a feeder magnet drum or in the form of proposed throw-feeder devices. It is known to arrange, within the supply reservoir, a screw with feeding elements which, during rotation of the screw, stir the mixture of developer powder on the one hand, and transport this mixture toward feeding means on the other hand. This screw is journalled by means of shaft lead-in portions in the side walls of the supply reservoir. Also with these shaft lead-in portions, which are generally below the level of the supply of developer powder, there exists the problem of a proper and wear-free seal.